Influence of Crystallization on the Conversion of Sm3+→Sm2+ in SrO–Bi2O3–K2O–B2O3 Glass‐Ceramics

Sm³⁺‐doped glass 13SrO–2Bi₂O₃–5K₂O–80B₂O₃ was fabricated by the conventional melt‐quenching technique. The glass‐ceramics were obtained by heating the as‐prepared glasses in air atmosphere at selected temperatures 550°C, 600°C, 615°C, and 650°C, respectively. The luminescence spectra of both Sm³⁺ and Sm²⁺ were detected in the ceramic heated at 650°C where crystalline phase is formed. The as‐prepared glass and the ceramics heated at 550°C, 600°C, and 615°C show only the emission due to Sm³⁺. In the sample heated at 650°C in air atmosphere, however, part of Sm³⁺ ions was converted to Sm²⁺, giving rise to sharp emission lines which are characteristic of Sm²⁺ in crystalline state. It is suggested that Sm²⁺ ions are located at Sr²⁺ site in the ceramic while Sm³⁺ ions are located at Bi³⁺ sites. The Sm²⁺‐doped glass‐ceramic has a high optical stability because the fluorescence intensity decreases by only about 8% of its initial value upon excitation at 488 nm Ar⁺ laser.     

Enhancement of the radiation resistance of cerium-containing fluorophosphate glasses through codoping with Sb2O3 and Bi2O3

The growing demand for radiation-resistant optical glasses for space and nuclear radiation applications has attracted significant research interest. However, radiation-resistant fluorophosphate glasses have been poorly studied. In this work, we report on the tailoring and performance of radiation-resistant fluorophosphate glasses that contained cerium through codoping with Sb₂O₃ and Bi₂O₃. The physical properties, optical properties, microstructure, and defects of fluorophosphate glasses were investigated using transmittance measurements, absorption measurements, as well as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results showed that the radiation resistance of all codoped fluorophosphate glasses was better than the undoped cerium-containing fluorophosphate glasses after 10–250 krad(Si) irradiation. Especially in glasses doped with Bi₂O₃, the optical density increment at 385 nm was only 0.1482 after 250 krad(Si) irradiation. The CeO₂ prevented the development of phosphate-related oxygen hole center (POHC) defects, whereas further codoping with Bi₂O₃ suppressed the formation of oxygen hole center (OHC) and POEC defects, reducing the breaking of phosphate chains caused by CeO₂. Bi³⁺ is more likely than Sb³⁺ to change the valence, affecting the transition equilibrium of intrinsic defects and reducing the concentration of defects produced by irradiation. When codoping with Sb₂O₃ and Bi₂O₃, Bi₂O₃ does not enhance radiation resistance owing to the scission effect of Sb₂O₃ on the phosphate chain, which is not conducive to the radiation resistance of glasses. This indicates that the cerium-containing fluorophosphate glasses doped with Bi₂O₃ can effectively suppress the defects caused by irradiation and improve the radiation resistance of the glasses.     

The System Bi2O,—B2O3

The phase diagram for the system Bi₂O₃-B₂O₃ has been determined experimentally. The melting point of Bi₂O₃ has been redetermined as 825° C with an estimated overall uncertainty of about ±3°C, and the molal heat of fusion of Bi₂O₃, calculated from the slope of the liquidus curve, is 2050 cal per mole. The system contains a body-centered cubic phase of approximate composition 12Bi₂O₃·B₂O₃, which melts incongruently at 632°C. Four congruently melting compounds exist in the system: 2Bi₂O₃· B₂O₃·5B₂O₃, Bi₂O₃·3B₂O₃, and Bi₂O₃·4B₂O₃, with melting points, respectively, of 675°, 722°, 708°, and 715°C. The Bi₂O₃·4B₂O₃ compound exhibits a sluggish transformation at 696°C. Compositions containing up to 97.5 wt% (85 mole %) Bi₂O₃ can be partly or totally quenched to glass. Indices of the quenched glasses are greater than 1.74. A region of liquid immiscibility extends at 709°C from almost pure B₂O₃ to 19.0 mole % Bi₂O₃. The extent of immiscibility theoretically calculated agrees with the experimentally determined value when 1.20 A is used for the ionic radius of Bi³⁺.     

Characterization of Bi2O3 thin films for doping photoluminescent Er3+ ions

Undoped and Er³⁺-doped Bi₂O₃ thin films were sputter-deposited on Si(100) substrates. Sufficiently oxidized Bi₂O₃ films with refractive indices between 2.17?2.23 were obtained at a wavelength of 633 nm; these values are comparable to those of bulk Bi₂O₃ crystals. While the film composition was stable for deposition temperatures between room temperature (RT) and 450 °C, the refractive index steeply decreased above 450 °C and reached 1.4 at 600 °C. The lowering of the optical transmittance spectra indicated aggregation of metallic Bi and darkening of the film. All films exhibited X-ray diffraction patterns of α-Bi₂O₃. The direct and indirect bandgap energies derived from the Tauc plots were 3.4–3.7 eV and 1.9–2.5 eV, respectively, depending on the O₂ flow rate and deposition temperature. Upon excitation of Er³⁺-doped Bi₂O₃ films at 532 nm, Er³⁺ emissions peaking at 1537 and 1541 nm appeared, and the photoluminescence spectra included fine structures reflecting crystal-field splitting. Resonant excitation of Er³⁺ 4f levels and indirect excitation via the defect levels of Bi₂O₃ followed by energy transfer to Er³⁺ contributed to the emission. The films deposited at RT with Er concentrations of 2 at.% had the emission intensity of Er³⁺, but concentration quenching strongly suppressed the Er³⁺ emission because the doped Er³⁺ ions stayed inside the Bi₂O₃ crystals. At deposition temperatures above 400 °C, the concentration quenching was mitigated possibly because out-diffusion of Er³⁺ ions reduced the effective number of Er³⁺ ions in the Bi₂O₃ crystalline domains.     

Effects of Sb2O3 on the microstructure and electrical properties of ZnO–Bi2O3-based varistor ceramics fabricated by two-step solid-state reaction route

In this work, the ZnO–Bi₂O₃–Cr₂O₃–Co₂O₃–MnO₂ varistors doped with different content of Sb₂O₃ were prepared by two-step solid-state reaction route, including a pre-calcining of the mixtures of nanosized ZnO and the other additives at an optimized temperature, followed by a consequent sintering process at different temperatures. Meanwhile, the effects of Sb₂O₃ on the sintering temperature, microstructure and electrical properties of the objective varistors were investigated. It was found the densification temperature went up in a proper range and the content of pyrochlore phase, spinel phase and β-Bi₂O₃ phase increased with the increasing content of Sb₂O₃, while the grain size of ZnO–Bi₂O₃-based varistor reduced. The results demonstrated that at the same sintering temperature, the second particles increased with the increasing amount of Sb₂O₃, which was helpful to control the grain growth, leading to a higher breakdown voltage. However, the decrease of α-Bi₂O₃ phase (melting point of α-Bi₂O₃ phase is 825 °C), which is the main component of the liquid Bi₂O₃ phase in the sample during sintering process, leads to the increase of the sintering temperature of the green pallet. As a result, the ZnO varistor doped with 3.0 mol% Sb₂O₃ sintered at 1000 °C exhibited the highest breakdown voltage of 1863.3 V/mm. By contrast, the ZnO varistor without Sb₂O₃ doping sintered at 900 °C had the optimum nonlinear coefficient of 59.8.     

White luminescence of bismuth and samarium codoped Y2O3 phosphors

In this work Sm³⁺ (0–2.0 at%) and Bi³⁺ (0–2.0 at%) doped Y₂O₃ luminescent powders were prepared by a sol–gel method from yttrium acetylacetonate, samarium and bismuth nitrates as metal sources. The as prepared powders (chemical composition is close to stoichiometric Y₂O₃) present the cubic structure from 700 °C, and at 900 °C are characterized by the presence of rounded particles with heterogeneous size of 42.9 nm. Luminescent effect of ions of Sm³⁺ and Bi³⁺ into Y₂O₃ host as was studied on heat treated powders from 800 to 1100 °C. The combination of the red luminescence from the Sm³⁺ ions and the bluish from Bi³⁺, makes the synthesized phosphors candidates to be used in fabrication of phosphor-converted light-emitting diodes (LEDs).     

Near-UV light excited Eu3+, Tb3+, Bi3+ co-doped LaPO4 phosphors: Synthesis and enhancement of red emission for WLEDs

A series of single-phase Eu³⁺, Tb³⁺, Bi³⁺ co-doped LaPO₄ phosphors were synthesized by solid-state reaction at 800 °C. Crystal structures of the phosphors were investigated by X-ray diffraction (XRD). A monoclinic phase was confirmed. The excitation (PLE) and emission (PL) spectra showed that the phosphors could emit red light centered at 591 nm under the 392 nm excitation, which is in good agreement with the emission wavelength from near-ultraviolet (n-UV) LED chip (370–410 nm). The results of PLE and PL indicated that the co-doped Tb³⁺ and Bi³⁺could enhance emission of Eu³⁺ and the fluorescent intensities of the phosphors excited at 392 nm could reach to a maximum value when the doping molar concentration of Tb³⁺ and Bi³⁺ is about 2.0% and 2.0%, respectively. The co-doping Tb³⁺ and Bi³⁺ ions can strengthen the absorption of near UV region. They can also be efficient to sensitize the emission of Eu³⁺, indicating that the energy transfer occurs from Tb³⁺ and Bi³⁺ to Eu³⁺ ions. From further investigation it can be found that co-doping Tb³⁺ and Bi³⁺ ions can also induce excitation energy reassignment between ⁵D₀–⁷F₁ and ⁵D₀–⁷F₂ in these phosphors, and result in more energy assignment to ⁵D₀–⁷F₂ emission in LaPO₄:Eu³⁺, Tb³⁺, Bi³⁺. Our research results displayed that La_0.94PO₄:Eu³⁺_0.02, Tb³⁺_0.02, Bi³⁺_0.02 could be a new one and could provide a potential red-emitting phosphor for UV-based white LED.     

Ternary doping of Na+, Bi3+ and La3+ to improve piezoelectric constant and electrical resistivity simultaneously in calcium bismuth niobate ceramics

High Curie-temperature layer-structured calcium bismuth niobate (CaBi₂Nb₂O₉) piezoelectric ceramics are promising for important application in high-temperature vibration sensors. However, such application is currently limited due to not only poor high-temperature piezoelectric constant (d₃₃), which is attributable to spontaneous polarization along a-b plane and high coercive fields, but also inferior high-temperature electrical resistivity, which results from volatilization of Bi₂O₃ during the sintering process that increases defect concentration of oxygen vacancies. Herein, we report a Na⁺, Bi³⁺ and La³⁺ ternary-doping-strategy to obtain Ca_0.8(Na_0.5La_0.3Bi_0.2)_0.2Bi₂Nb₂O₉ ceramics, which exhibited higher piezoelectric constant and larger electrical resistivity as accompanied by a better thermal stability at high-temperatures. The piezoelectric constant was enhanced from 8.8 pC/N in pristine CaBi₂Nb₂O₉ to 13.4 pC/N in Ca_0.8(Na_0.5La_0.3Bi_0.2)_0.2Bi₂Nb₂O₉ ceramics, which is ascribed to the presence of pseudo-tetragonal structural distortion after La³⁺ doping. In addition, the electrical resistivity at 600 °C was increased by more than one-order of magnitude from 3.7 × 10⁴ Ω cm in pristine CaBi₂Nb₂O₉ to 1.4 × 10⁶ Ω cm in Ca_0.8(Na_0.5La_0.3Bi_0.2)_0.2Bi₂Nb₂O₉ ceramics. Such significant improvement in electrical resistivity results from the reduction in oxygen vacancies due to ternary doping of Na⁺, Bi³⁺ and La³⁺ and stronger binding interaction between La³⁺ dopants and O^2? in (Bi₂O₂)²⁺ layers in Ca_0.8(Na_0.5La_0.3Bi_0.2)_0.2Bi₂Nb₂O₉ ceramics. This work demonstrates an important way of employing chemical doping to improve piezoelectric constant and electrical resistivity simultaneously at high-temperatures to tune structural distortion in bismuth-layered structural CaBi₂Nb₂O₉ ceramics.     

Properties of Bismuth-Containing High-Silica Glass Depending on the Bismuth Concentration and Heat Treatment. I. Spectral-Optical Properties

Bismuth-containing high-silica glass is synthesized by impregnating porous glass matrices in 0.01–0.5 M aqueous solutions of bismuth nitrate with the subsequent heat treatment at a temperature of 50–875°C. The dependences of the spectral-optical properties of the synthesized glass on the concentration of the doped bismuth (0.02–1.17 wt % Bi₂O₃) and heat treatment temperature are studied. It is found using the method of optical spectroscopy that bismuth is present in glass in different oxidation states—Bi³⁺, Bi²⁺, and \(\rm{Bi_5^{3+}}\) clusters. Near infrared spectroscopy in the 7500–4000 cm^–1 frequency range reveals that an increase in the temperature results in a gradual decrease in the intensity of the absorption bands due to the vibration of hydroxyl groups and water molecules adsorbed on the surface. The glasses (T ~ 50 and 400°C) exhibit bands at 4445–4443, 4433, and 4417–4415 cm^–1, which correspond to the absorption of Bi⁺ ions.     

Study on the properties of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-BaO lead-free glass using in the electronic pastes

The Sb₂O₃ doping lead-free glass in Bi₂O₃-B₂O₃-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through the process of water quenching. Glass transition temperatures (T _g ), glass soften temperatures(T _s ), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures range of 25–300°C (α_25–300) were measured for subsystems along with the different ratio of Bi₂O₃, B₂O₃ and BaO. For these subsystems, T _g ranged from 458 to 481°C, and T _s ranged from 490 to 512°C, both decreasing with the increasing of Bi₂O₃/B₂O₃ ratio, and increasing with the increasing of BaO/B₂O₃ ratio. The measured α_25–300 ranged from 65.3 to 76.3 × 10⁻⁷ K⁻¹, with values increasing with increasing Bi₂O₃/B₂O₃ and BaO/B₂O₃ ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated from 10¹³ to 10¹¹ Ω cm with the temperature varied from 80–200°C. The structure of Bi₂O₃-B₂O₃-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO₆], [BO₃], and [BO₄] basic structural units, and it appears that Ba²⁺ acts as a glass-modifier in this ternary system, but the Bi³⁺ has entered the glass network when it is in relative high content so as to change the α_25–300, T _s and T _g .     

Improving the luminescence and afterglow properties of Mg3Y2Ge3O12:Cr3+ by co-doping Bi3+

Generally, the emission intensity and afterglow of the near infrared phosphors can be improved by co-doping the sensitizer. In this work, Bi³⁺ ions as sensitizer are introduced into the near infrared phosphor Mg₃Y₂Ge₃O₁₂:Cr³⁺, and the luminescence properties are investigated. According to the principle of radius adaptation, Bi³⁺ ions would occupy eight coordinates in the host instead of Y³⁺ and Mg²⁺. Through structural refinement, theoretical calculation and experimental phenomena, there are two kinds of luminescent sources for Bi³⁺ ions, which come from ³P₁ → ¹S₀ (441 nm) and MMCT (330 nm), respectively. In addition, the substitution of Bi³⁺ for Mg²⁺ will result in inequivalent substitution forming defects (Bi_Mg·), and the trap depth is 0.55 eV. For Bi³⁺ and Cr³⁺ co-doped Mg₃Y₂Ge₃O₁₂, there are two factors can that can affect the luminescent properties of Cr, which are energy transfer and defects. The samples are obtained with three times the original emission intensity with the introduction of defects. At the same time, Bi³⁺ ions capture electrons to form new electron traps Bi²⁺ (Bi³⁺ + e^-) and the trap depth is 0.81 eV. Therefore, under the action of two traps Bi_Mg· and Bi²⁺ (Bi³⁺ + e^-), the afterglow characteristics of the samples are improved and the time can reach 1.5 h.     

Red-emitting enhancement of Bi4Si3O12:Sm3+ phosphor by Pr3+ co-doping for White LEDs application

In this account, Bi₄Si₃O₁₂:Sm³⁺ and (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) red phosphors were prepared by solution combustion method fueled by citric acid at 900 °C for 1 h. The effects of co-doping Pr³⁺ ions on red emission properties of Bi₄Si₃O₁₂:Sm³⁺ phosphors, as well as the mechanism of interaction between Sm³⁺ and Pr³⁺ ions were investigated by various methods. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) revealed that smaller amounts of doped rare earth ions did not change the crystal structure and particle morphology of the phosphors. The photoluminescence spectroscopy (PL) indicated that shape and position of the emission peaks of (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors excited at λ_ex=403 nm were similar to those of Bi₄Si₃O₁₂:Sm³⁺ phosphors. The strongest emission peak was recorded at 607 nm, which was attributed to the ⁴G_5/2→⁶H_7/2 transition of the Sm³⁺ ion. The photoluminescence intensities of Bi₄Si₃O₁₂:Sm³⁺ phosphors were significantly improved by co-doping with Pr³⁺ ions and were maximized at Sm³⁺ and Pr³⁺ ions doping concentrations of 4 mol% and 0.1 mol%, respectively. The characteristic peaks of Sm³⁺ ions were displayed in the emission spectra of (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors excited at respectively λ_ex=443 nm and λ_ex=481 nm (Pr:³H₄→³P₂, ³H₄→³P₀). This indicated the existence of Pr³⁺→Sm³⁺ energy transfer in (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors.     

Selective oxidation of hydrogen sulfide containing excess water and ammonia over Bi-V-Sb-O catalysts

We investigated the selective oxidation of hydrogen sulfide to elemental sulfur and ammonium thiosulfate by using Bi₄V_2-xSb_xO_11-y catalysts. The catalysts were prepared by the calcination of a homogeneous mixture of Bi₂O₃, V₂O₅, and Sb₂O₃ obtained by ball-milling adequate amounts of the three oxides. The main phases detected by XRD analysis were Bi₄V₂O₁₁, Bi_1.33V₂O₆, BiSbO₄ and BiVO₄. They showed good H₂S conversion with less than 2% of SO₂ selectivity with a feed composition of H₂S/O₂/NH₃/H₂O/He=5/2.5/5/60/27.5 and GHSV=12,000 h^-1 in the temperature ranges of 220–260 ‡C. The highest H₂S conversion was obtained for x=0.2 in Bi₄V_2-xSb_xO_11-y catalyst. TPR/TPO results showed that this catalyst had the highest amount of oxygen consumption. XPS analysis before and after reaction confirmed the least reduction of vanadium oxide phase for this catalyst during the reaction. It means that the catalyst with x=0.2 had the highest reoxidation capacity among the Bi₄V_2-xSb_xO_11-y catalysts.     

Rapid microwave sintering of zinc oxide-based varistor ceramics

Samples of ZnO + Bi₂O₃ + Sb₂O₃ varistor ceramics were microwave sintered using gyrotron systems operating at a frequency of 24 GHz. The microwave power was automatically regulated to implement heating at a constant heating rate of 10–130 °C/min up to a temperature of 1100–1300 °C with no isothermal hold. The final sintered density of the samples was 95–96 % of the theoretical value. Manifestations of the thermal instability associated with the liquid phase formation were observed at a temperature of about 600 °C. The estimated volumetrically absorbed power density at the onset of instability was ≥20 W/cm³, and the temperature difference measured between the center and periphery of the samples reached 200 °C. Correlation has been revealed between the thermal instability occurrence and the shift of densification curves towards lower temperatures. A mechanism underlying enhanced densification in electromagnetic field-assisted sintering processes is suggested.     

Enhanced electrocatalytic activity and CO2 tolerant Bi0.5Sr0.5Fe1-xTaxO3-δ as cobalt-free cathode for intermediate-temperature solid oxide fuel cells

One of the significant motivations in developing intermediate-temperature solid oxide fuel cells (IT-SOFCs) is to design cobalt-free cathodes with high electrocatalytic activity and CO₂ tolerance ability. In this work, iron-based perovskite materials Bi_0.5Sr_0.5Fe_1-xTa_xO_3-δ are investigated as potential cathodes for IT-SOFCs. The effects of Ta doping on crystal structure, thermal expansion coefficients and electrocatalytic activities are systematically evaluated. Among the Ta-doped oxides, Bi_0.5Sr_0.5Fe_0.9Ta_0.1O_3-δ exhibits the highest electrochemical performance with the lowest polarization resistance (R_p) of 0.124 Ω cm² at 700 °C in air. The peak power density of the single cell with Bi_0.5Sr_0.5Fe_0.9Ta_0.1O_3-δ cathode reaches 1.36 W cm⁻² at 700 °C. Compared to Bi_0.5Sr_0.5FeO_3-δ, the improved CO₂ tolerance of Ta-doped oxides can be attributed to the high acidity of Ta⁵⁺ cations and the increased average metal bond energy (ABE) within the material. Further study proves that the adsorption-dissociation process of molecular oxygen is the limiting step for oxygen reduction reaction (ORR) on Bi_0.5Sr_0.5Fe_0.9Ta_0.1O_3-δ cathode.     

Structural and physical characteristics of Au2O3-doped sodium antimonate glasses – Part I

Na₂O-Sb₂O₃ glasses doped with different concentrations of Au₂O₃ were prepared by melt quenching technique and later were heat treated at 800°C for 6 hours. Structural analysis by XRD, XPS, SEM, EDS, and DSC techniques indicated that the samples are embedded with multiple crystallites composed of Sb³⁺, Sb⁵⁺, Au³⁺ ions, and Au⁰ metallic particles. These studies have further demonstrated a gradual increasing fraction of Au⁰ metallic particles with increasing Au₂O₃ concentration. IR spectral studies suggested increasing the degree of polymerization of the glass network (due to increasing concentration of Sb⁵⁺ ions that participate in the glass network with Sb^VO₄ structural units) with rise in the concentration of Au₂O₃. Optical absorption spectra of the titled samples have exhibited a broad absorption band at about 530 nm predicted due to the surface plasmon resonance (SPR) and exhibited a spectral red shift with increasing intensity with increase in Au₂O₃ content. Photoluminescence (PL) spectra of the samples recorded (at λ_exc = corresponding SPR band position) exhibited an emission peak at about 580 nm (identified as being due to interband transition between sp and d bands of gold particles). Overall, the analysis of these results has confirmed increasing concentration of Au metallic particles with increase in Au₂O₃ content in the titled material. Finally, it is predicted that the presence of higher concentration of gold particles in the polymerized antimonate glass network makes the materials useful for designing different nano dimensional optoelectronic devices.     

Luminescence and self-referenced optical temperature sensing performance in Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors

Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca₂YZr₂Al₃O₁₂:Bi³⁺ samples, energy transfer from Bi³⁺ to Eu³⁺, and the temperature sensing properties of Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples have been systematically researched. Under the excitation of ultraviolet light, Bi³⁺ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi³⁺ instead of Ca²⁺ and Y³⁺ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu³⁺ content in Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K^-1 and 0.664 %K^-1, respectively. All above results suggest that Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphor is a potential alternative for optical thermometer.     

An experimental study and WinXCom calculations on X-ray photon characteristics of Bi2O3- and Sb2O3-added waste soda-lime-silica glass

Radiation is used in a variety of different fields, and thus protection from its hazardous effects become a popular subject for researchers. For this purpose, in the present study, waste soda-lime-silica glasses as SiO₂–Na₂O–CaO–Bi₂O₃ and SiO₂–Na₂O–CaO–Sb₂O₃ were investigated for X-rays photon characteristics in the energies of 0.01–0.1 MeV via WinXCom program, and the results were compared with the experimental findings obtained at 0.04 MeV. Waste packaging glass was evaluated by adding varying amounts (0.005, 0.05, and 0.5 percentages) of Bi₂O₃ and Sb₂O₃. Seven different glass batches were prepared by following the procedures of precisely weighing the relevant amounts to obtain 10 g specimen in total, homogeneously mixing the respective contents, and thoroughly melting in an Au–Pt crucible via conventional electrical furnace at 1250 °C for 4 h. The linear attenuation coefficient (LAC) for glass specimens were experienced at 0.04 MeV, and it was found out that increasing contents of both oxides increased the LAC implying that a decrease in X-ray transmission occurred. From the point of WinXCom calculations, the LAC and mass attenuation coefficient (MAC) increased while half value layer (HVL) and mean free path (MFP) thicknesses decreased as the oxide substances increased in the glass specimens. That is, Sb₂O₃ addition provided higher X-rays attenuation characteristics in comparison to Bi₂O₃ additive. Further, the experimental data at 0.04 MeV were compared with WinXCom calculations, and it was figured out that the data were parallel for each other, but the correlation coefficient (R²) was found as 0.15 which means that the values were in loose agreement.     

Stabilized β-Bi2O3 nanoparticles from (BiO)4CO3(OH)2 precursor and their photocatalytic properties under blue light

Stabilized tetragonal Bi₂O₃ nanoparticles (β-Bi₂O₃) were obtained by annealing treatments of amorphous Bi-based precursors, obtained by chemical precipitations, at temperatures between 350 and 450?°C. The formation of the stabilized β-Bi₂O₃ phase was possible by using (BiO)₄CO₃(OH)₂ while other precursors such as amorphous bismuth carbonate ((BiO)₂CO₃) and amorphous basic bismuth nitrate (Bi₆O₆(OH)₂(NO₃)₄·2H₂O) led to the formation of the thermodynamically stable monoclinic α-Bi₂O₃ and Bi₅O₇NO₃ phases. The Bi-based precursors were prepared by the chemical precipitation method at room temperature in ethylenediamine-solvent varying the HNO₃/Bi³⁺ molar ratio (10, 26 and 56). The physicochemical properties of the three as-prepared amorphous precursors and the formed-after-calcination β-Bi₂O₃, α-Bi₂O₃ and Bi₅O₇NO₃ phases were analyzed by X-ray diffraction, scanning electron microscopy, thermogravimetry, X-ray photoelectron spectroscopy (XPS), FTIR analysis, diffuse reflectance spectroscopy and surface area by BET method. The photocatalytic activity of all annealed solids containing the β-Bi₂O₃ phase was tested in the photodegradation of the indigo carmine (IC) dye under specific blue light. A schematic diagram of the Bi₂O₃ phases obtained as a function of the annealing conditions and initial amorphous precursor is proposed and explained in terms of the amount of CO₃^2-, NO₃^- and amine (ENH₂²⁺ ? ENH⁺) ions present in each bismuth precursor.     

Phase development in ZnO varistors

Based on a typical ZnO varistor composition (97·0 mol.-% ZnO, 1·0 mol.-% Bi₂O₃, 1·0 mol.-% Sb₂O₃, 0·5 mol.-% MnO and 0·5 mol.-% Co₃O₄), phase development of the ZnO varistor during sintering has been investigated using in situ high temperature X-ray diffraction up to 900°C, and conventional ambient X-ray diffraction for samples sintered at 900°C to 1250°C. The results indicate that α-Bi₂O₃ can be detected until 700°C; the pyrochlore phase can be detected in the samples heat treated at 700°C and up to 1250°C; the spinel phase is present at and >900°C. However, the main phases in the varistor are established by 950°C. By this temperature, the essential microstructure features are formed, and the varistors exhibit non-linear electrical properties, with a non-linear coefficient α of 35 and breakdown field of 8000 V cm^?1. With increasing sintering temperature, both the α value and breakdown field decrease.